An Iranian user reported that there is the threat of man-in-the-middle attacks using a fake SSL certificate that was circulating as of Aug. 29. The fake certificate, which was legitimately signed, was displayed when logging into Google's Gmail.

Mozilla will be releasing new versions of Firefox, Firefox Mobile and Thunderbird
to revoke certificates signed by DigiNotar after reports of at least
one fake SSL certificate from DigiNotar for various Google services.

Google will also mark DigiNotar untrusted in the next release of the Chrome OS (Chromium). Microsoft followed suit by removing DigiNotar from the default certificates store on Windows 7, Vista, Server 2008 and 2008 R2.

A user "alibo" posted on Google's Help forum
on Aug. 28 a screenshot of a SSL certificate warning that it appeared
in Chrome while accessing Gmail. The warning didn't appear when "alibo"
tried to access Gmail over a VPN connection. Alibo claimed the warning
came up only with google.com domains and not for Yahoo or Bing.

Alibo's post included a link to text-sharing site Pastebin with the
contents of the fake SSL certificate for Gmail.com as viewed on Aug.
27. The certificate was issued by DigiNotar, an official Dutch
certification authority, on July 10, meaning the fake certificate was
valid for at least five weeks. The certificate was revoked by the Dutch
CA on Aug. 29 at 16:59:03 GMT.

Chester Wisniewski, a senior security advisor at Sophos, speculated on the Naked Security blog
that the new versions from Google and Mozilla were "because DigiNotar
has not explained how the Google certificate was signed and to prevent
further abuse."

DigiNotar validates and registers certificates for various government
and professional sites in the Netherlands. DigiNotar was acquired by
VASCO Data Security International in January of this year. VASCO did
not respond to eWEEK's requests for comment or explanation as to what
may have happened.

"I think my ISP or my government did this attack (because I live in
Iran and you may hear something about the story of Comodo hacker!)"
alibo wrote. Alibo's internet service provider was ParsOnline, but
claimed on the forum that a friend on a different ISP was seeing the
same problem.

Earlier in the year, Comodo, a certificate authority in the United States, was tricked into issuing fake SSL certificates
for a handful of sites, including Google, Skype and Yahoo, when an
attacker managed to obtain a reseller's login credentials. Comodo
revoked the certificates immediately before it could be used.

The DigiNotar certificate was valid, but there was "no hard evidence
about the origin of the attack," Kaspersky Labs' Roel Schouwenberg told
eWEEK. The certificate could be used to eavesdrop on and potentially
hijack user sessions on all Google services using SSL, including Gmail,
secure search and Google+. The fact that DigiNotar had ties with
government agencies made this "an even trickier situation,"
Schouwenberg said.

It's unclear at this time how widespread the problem was or who has been affected.
Even though the certificates have been revoked, the fake ones can still
cause problems for users as not all browsers check certificates against
the revoked list by default. Other browsers have not yet followed
Mozilla's footsteps, but users would be "prudent" to remove DigiNotar
from the trusted certificates list on the Web browser until there is
further clarification, Wisniewski recommended. He noted, however, that
Mozilla's decision could pose issues for Websites who have legitimately
purchased certificates from DigiNotar, Wisniewski said.

Security researchers were in an uproar, trying to figure out what may
have happened. DigiNotar is not saying whether it had been compromised,
whether attackers had managed to steal the keys necessary to sign their
own certificates or if it was tricked into signing the certificate for
someone pretending to be Google.

"I think it might still be a stretch to attribute this to the Iranian government," said Moxie Marlinspike on Twitter. "We all know how that went last time."

Marlinskpike had discussed problems with SSL and the trust system at
Black Hat earlier this month and introduced a new project Convergence
to create a new system of user-defined notaries instead of relying on
the certificate authorities.

"It is simply more evidence that the current CA infrastructure that we
have decided to "trust" is totally untrustworthy. It doesn't matter how
this happened, it has happened before and unfortunately will happen
again," Wisniewski said before encouraging users to download
Marlinspike's Firefox plugin and bypass certificate authorities
altogether.

"Placing trust in more than 600 certificate authorities to be honest and not screw up is quite a leap of faith," he said.